The present invention relates to the art of oil and/or lubricant diagnostics. It finds particular application in conjunction with diesel engines such as those employed in off-highway vehicles, e.g., railroad locomotives, mining vehicles and machinery, etc. It will be described with particular reference thereto. However, it is to be appreciated that the present invention is also amenable to other internal combustion engines and the like which employ lubrication systems for various applications, be it off-highway applications, on-highway applications, or otherwise.
Maintenance of engine lubricant quality is essential to the proper operation and long service life of an internal combustion engine. A responsibility of the engine operator or maintenance personnel is to periodically check the lubricant and, if needed, add an appropriate amount of fresh lubricant or change the lubricant entirely to maintain the lubricant in the engine at a desired quality level. As used herein, the term xe2x80x9cfresh lubricantxe2x80x9d includes a base lubricant (e.g., a natural oil, a synthetic oil, or the like) containing desired quantities and types of lubricant additives or adjuncts.
In general, the quality of the lubricant in an engine degrades with engine use. Lubricant degradation occurs due to depletion of lubricant additives that perform specific functions such as control viscosity, reduce wear, increase lubricity, minimize deposits, prevent oxidation, and other desirable features. Lubricant degradation can also occur by the ingestion of foreign materials into the lubricant such as dirt from the surrounding environment, wear materials from the engines that occur as part of the natural operating process, and blow-by from the combustion process. Lubricant degradation can also occur due to a break-down of the base stock of the lubricant. In the extreme case fuel or water/coolant contamination of the lubricant can cause lubricant degradation.
Two ways of improving the quality of the engine lubricant is to periodically remove some or all of the engine lubricant and replace it with fresh lubricant. Also, in most cases filters are used to remove foreign materials above a certain size from the engine lubricant. Various systems have been proposed for periodically removing a given quantity of lubricant from the engine and either storing the lubricant until it can properly be disposed of, or in the case of a diesel engine, optionally periodically injecting the lubricant into the fuel tank where the lubricant is mixed with the fuel and then burned in the engine along with the fuel. Also, it is generally known to provide such systems with automatic lubricant level sensing devices which maintain the proper level of lubricant in the engine.
In some systems, a given quantity of the engine lubricant is removed at preset time intervals based on engine usage factors. In others, small increments of engine lubricant are periodically removed and substantially simultaneously replaced with correspondingly small increments of fresh lubricant. In still others, a given amount of engine lubricant is periodically removed based on sensors that measure different operating variables of the engine such as the level, temperature and/or pressure of the lubricant within the engine, the number of engine starts or crank shaft revolutions, the length of time the engine has been in motion and at rest, engine temperature, fuel consumption, etc. See, e.g., U.S. Pat. No. 5,749,339 to Graham, et al.
However, many previously developed lubrication systems are characterized by certain limitations and/or drawbacks. For example, systems that employ a set periodic maintenance schedule can have less than optimized engine operation time due to unnecessary maintenance down time. Likewise, systems that employ a maintenance schedule based on engine operation and/or operating conditions can also experience the same problem insomuch as these factors, while perhaps indicative, do not directly reflect the lubricant quality. Therefore, estimates of the lubricant""s amount of degradation are imprecise and maintenance or lubricant exchanges may be prematurely scheduled. In addition to unnecessary down time, prematurely scheduled maintenance or lubricant exchanges result in unnecessary lubricant consumption. On the other hand, late maintenance or lubrication exchange is even less desirable insomuch as it can result in unnecessary engine wear, reducing engine life, and possible engine failure. Consequently, the previously developed lubrication systems tended to error on the side of premature maintenance and/or premature lubrication exchange.
Moreover, the previously developed systems did not account for or detect conditions which may prompt lubricant failure, such as, e.g., incipient failure detection (IFD) denoted by significant water/coolant contamination and/or fuel contamination of the lubricant. Preset maintenance schedules and maintenance schedules based on engine operation and/or operating conditions do not anticipate lubricant failure due to unexpected contamination.
Accordingly, there is a need for a system that more effectively determines the condition and thus the quality of the engine lubricant, such that when the quality of the engine lubricant degrades a predetermined amount or incipient failure is detected, appropriate corrective or otherwise responsive actions may be taken.
The present invention contemplates a new continuous on-board diagnostic lubricant monitoring system and method which at least partially overcomes the above-referenced problems and others.
In accordance with one aspect of the present invention, a method of monitoring a lubricant is provided. The method includes the steps of measuring the lubricant""s temperature, and measuring the lubricant""s permittivity. After temperature dependence in the permittivity has been compensated for, it is determined if the lubricant has been contaminated by water or other coolant.
In accordance with a more limited aspect of the present invention, the method also includes determining a rate of change of the lubricant""s permittivity for a first period of time, and determining a rate of change of the lubricant""s temperature for a second period of time. The lubricant is then determined to be contaminated by a coolant if the rate of change of the lubricant""s permittivity for the first period of time is greater than a first threshold, and an absolute value of the rate of change of the lubricant""s temperature for the second period of time is less than a second threshold.
In accordance with a more limited aspect of the present invention, the first and second periods of time are the same.
In accordance with a more limited aspect of the present invention, the method also includes determining a rate of change of the lubricant""s temperature for a third period of time, where the third period of time is greater than the first and second periods of time. In this case, for a determination to be made that the lubricant is contaminated by a coolant, it has to also be found that the rate of change of the lubricant""s temperature for the third period of time is less than a third threshold
In accordance with a more limited aspect of the present invention, the method also includes selecting a minimum temperature from those used to determine the rate of change of the lubricant""s temperature for the second time period. In this case, for a determination to be made that the lubricant is contaminated by a coolant, it has to also be found that the minimum temperature is greater than a threshold temperature.
In accordance with another aspect of the present invention, a method of monitoring a lubricant includes obtaining, over time, permittivity data from measured permittivity values of the lubricant. Based on changes in the permittivity data over time, a rate of degradation of the lubricant""s quality is determined, and an amount of time until the lubricant reaches a set degraded quality level is further determined.
In accordance with a more limited aspect of the present invention, the method also includes determining if the lubricant has been changed or topped-off by detecting changes in the permittivity data which exceed a threshold level.
In accordance with a more limited aspect of the present invention, the amount of time until the lubricant reaches the set degraded quality level is given by:
(cond_limitxe2x88x92current_perm)/perm_slope 
where, cond_limit represents a condemning limit defined by the lubricant""s permittivity when the lubricant has reach the set degraded quality level; current_perm represents the lubricant""s current determined permittivity; and perm_slope represents the determined rate of degradation of the lubricant""s quality based on changes in the permittivity data.
In accordance with a more limited aspect of the present invention, the current determined permittivity of the lubricant is a median of a plurality of most recently obtained permittivity data.
In accordance with another aspect of the present invention, a lubrication system for an engine is provided. The lubrication system includes a lubricant, and a diagnostic cell which samples the lubricant for diagnostic testing thereof. The diagnostic cell includes a permittivity sensor which monitors the lubricant""s permittivity, and a temperature sensor which monitors the lubricant""s temperature.
In accordance with a more limited aspect of the present invention, the diagnostic cell further includes a manifold in which the permittivity and temperature sensors are mounted. The manifold is arranged such that sampled lubricant is selectively made to encounter the permittivity and temperature sensors.
In accordance with a more limited aspect of the present invention, the lubrication system also includes a controller which interfaces with the diagnostic cell to carry out the diagnostic testing. The controller receives permittivity data from the permittivity sensor and temperature data from the temperature sensor.
In accordance with a more limited aspect of the present invention, the diagnostic testing carried out includes determining if the lubricant has been contaminated by a coolant.
In accordance with a more limited aspect of the present invention, the controller determines a rate of change of the lubricant""s permittivity for a first time period based on the permittivity data it receives, and the controller determines a rate of change of the lubricant""s temperature for a second time period based on the temperature data it receives. The controller determines that the lubricant has been contaminated by a coolant if the rate of change of the lubricant""s permittivity for the first time period is greater than a first threshold and an absolute value of the rate of change of the lubricant""s temperature for the second time period is less than a second threshold.
In accordance with a more limited aspect of the present invention, the controller further determines a rate of change of the lubricant""s temperature for a third time period based on the temperature data it receives. The third time period is longer than the first and second time periods. For the controller to determine that the lubricant has been contaminated by a coolant in this case, the controller has to also find that the rate of change of the lubricant""s permittivity for the third time period is less than a third threshold.
In accordance with a more limited aspect of the present invention, the controller further determines a minimum lubricant temperature for the second time period from the temperature data it receives. For the controller to determine that the lubricant has been contaminated by a coolant in this case, the controller has to also find that the minimum lubricant temperature is greater than a threshold temperature.
In accordance with a more limited aspect of the present invention, the controller determines a time to condemning limit for the lubricant based on the permittivity data received. In accordance with a more limited aspect of the present invention, the time to condemning limit is given by:
(cond_limitxe2x88x92current_perm)/perm_slope 
where, cond_limit represents a condemning limit defined by the lubricant""s permittivity when the lubricant has reach a selected level of degradation; current_perm represents the lubricant""s current determined permittivity; and perm slope represents a rate of lubricant quality degradation as determined from the permittivity data.
In accordance with a more limited aspect of the present invention, the engine is either a railroad locomotive engine or a mining vehicle engine.
In accordance with another aspect of the present invention, a method of monitoring a lubricant is provided. The method includes obtaining measurements of the lubricant""s viscosity and temperature. The viscosity measurements are then normalized based on the temperature measurements such that the normalized viscosity measurements all relate to a common reference temperature. Finally, a condition of the lubricant is diagnosed based on the normalized viscosity measurements.
In accordance with a more limited aspect of the present invention, the diagnosis includes diagnosing fuel contamination and lubricant xe2x80x9cshear downxe2x80x9d of the lubricant based on the normalized viscosity measurements.
In accordance with a more limited aspect of the present invention, the diagnosis includes distinguishing between different degrees of fuel contamination based on the normalized viscosity measurements.
In accordance with a more limited aspect of the present invention, the method also includes determining, based on the normalized viscosity measurements, a time to condemning limit for the lubricant due to fuel contamination.
In accordance with a more limited aspect of the present invention, the diagnosis includes diagnosing quality degradation of the lubricant based on the normalized viscosity measurements.
In accordance with a more limited aspect of the present invention, the method also includes determining, based on the normalized viscosity measurements, a time to condemning limit for the lubricant due to quality degradation.
In accordance with a more limited aspect of the present invention, the method also includes determining, based on the normalized viscosity measurements, a time to condemning limit for the lubricant.
In accordance with a more limited aspect of the present invention, the time to condemning limit is one of an upper viscosity limit under which it is desired that the lubricant""s viscosity remain, or a lower viscosity limit over which it is desired that the lubricant""s viscosity remain.
In accordance with another aspect of the present invention, a lubrication system for an engine includes a lubricant, and a diagnostic cell which samples the lubricant for diagnostic testing thereof. The cell includes a viscosity sensor which monitors the lubricant""s viscosity, and a temperature sensor which monitors the lubricant""s temperature. It is this temperature sensor that is utilized to normalize the viscosity measurement.
A controller interfaces with the diagnostic cell to carry out the diagnostic testing. The controller receives viscosity data from the viscosity sensor and temperature data from the temperature sensor. The viscosity and temperature data is processed to diagnose a condition of the lubricant.
In accordance with a more limited aspect of the present invention, the condition diagnosed is one of fuel contamination of the lubricant, or quality degradation of the lubricant. In accordance with a more limited aspect of the present invention, the viscosity data and the temperature data are processed to determine a time to condemning limit for the lubricant.
In accordance with a more limited aspect of the present invention, the viscosity sensor is a dynamic (rotational) viscocometer.
In accordance with a more limited aspect of the present invention, the lubrication system also includes a data link which transfers data between the lubrication system and a site remote from the lubrication system.
In accordance with a more limited aspect of the present invention, the lubrication system also includes a manifold in which the viscosity and temperature sensors are mounted. The manifold is arranged such that sampled lubricant is selectively made to encounter the viscosity and temperature sensors.
In accordance with a more limited aspect of the present invention, the lubrication system also includes indicating means for providing a human perceivable indication of the condition of the lubricant.
In accordance with a more limited aspect of the present invention, the lubrication system also includes a storage device in which the viscosity and temperature data are saved.
In accordance with a more limited aspect of the present invention, the lubrication system also includes lubricant refreshing means for selectively carrying out one or more functions in response to the diagnosed condition of the lubricant. The functions carried out include removing lubricant from the lubrication system, and/or adding fresh lubricant to the lubrication system.
In accordance with a more limited aspect of the present invention, the engine is a railroad locomotive engine, or a mining vehicle engine.
One advantage of the present invention is continuous on-board monitoring of engine lubricant quality.
Another advantage of the present invention is protection of the engine from excessive lubricant degradation and incipient lubricant failure due to unexpected contamination.
Still another advantage of the present invention is improved engine operation time. Another advantage of the present invention is lubricant conservation.
Still further advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.